Abstract

In the past, significant effort was placed in flow field measurements
of rotor wake vortices. This was driven by the importance of the rotor
blade tip vortices for the blade-vortex interaction noise radiation of
helicopters. The goal is to obtain reliable data for the generation of
a generalized model of tip vortices, including their generation and
roll-up, and their aging while passing through the rotor disk and
interacting with some of the revolving blades. In 2001 DLR, ONERA,
NASA Langley, US Army AFDD and DNW performed the HART II test in the
large low-speed facility of the DNW with a 40% Mach scaled model rotor
of the Bo105. Major emphasis was placed on three component particle
image velocimetry (3C-PIV) measurements of the blade tip vortices. They
were traced from their creation in the second and third quadrant of the
rotor disk to the rear of the rotor, including blade-vortex interaction
(BVI). This paper deals with difficulties associated with the analysis
of such 3C-PIV measurements and with the methodologies that need to be
applied to overcome these difficulties.